Virtual and augmented reality systems and methods

ABSTRACT

An imaging system includes a light source configured to generate a light beam. The system also includes first and second light guiding optical elements having respective first and second entry portions, and configured to propagate at least respective first and second portions of the light beam by total internal reflection. The system further includes a light distributor having a light distributor entry portion, a first exit portion, and a second exit portion. The light distributor is configured to direct the first and second portions of the light beam toward the first and second entry portions, respectively. The light distributor entry portion and the first exit portion are aligned along a first axis. The light distributor entry portion and the second exit portion are aligned along a second axis different from the first axis.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a continuation of U.S. patent applicationSer. No. 15/443,002, filed on Feb. 27, 2017 under attorney docket numberML.20059.00 and entitled “VIRTUAL AND AUGMENTED REALITY SYSTEMS ANDMETHODS,” which claims priority to U.S. Provisional Application Ser. No.62/301,502, filed on Feb. 29, 2016 under attorney docket numberML.30059.00 and entitled “VIRTUAL AND AUGMENTED REALITY SYSTEMS ANDMETHODS.” This application is related to U.S. Utility patent applicationSer. No. 14/331,218 filed on Jul. 14, 2014 under attorney docket numberML.20020.00 and entitled “PLANAR WAVEGUIDE APPARATUS WITH DIFFRACTIONELEMENT(S) AND SYSTEM EMPLOYING SAME,” U.S. Utility patent applicationSer. No. 14/555,585 filed on Nov. 27, 2014 under attorney docket numberML.20011.00 and entitled “VIRTUAL AND AUGMENTED REALITY SYSTEMS ANDMETHODS,” U.S. Utility patent application Ser. No. 14/726,424 filed onMay 29, 2015 under attorney docket number ML.20016.00 and entitled“METHODS AND SYSTEMS FOR VIRTUAL AND AUGMENTED REALITY,” U.S. Utilitypatent application Ser. No. 14/726,429 filed on May 29, 2015 underattorney docket number ML.20017.00 and entitled “METHODS AND SYSTEMS FORCREATING FOCAL PLANES IN VIRTUAL AND AUGMENTED REALITY,” U.S. Utilitypatent application Ser. No. 14/726,396 filed under on May 29, 2015 underattorney docket number ML.20018.00 and entitled “METHODS AND SYSTEMS FORDISPLAYING STEREOSCOPY WITH A FREEFORM OPTICAL SYSTEM WITH ADDRESSABLEFOCUS FOR VIRTUAL AND AUGMENTED REALITY,” and U.S. Prov. PatentApplication Ser. No. 62/156,809 filed under on May 4, 2015 underattorney docket number ML.30058.00 and entitled “SEPARATED PUPIL OPTICALSYSTEMS FOR VIRTUAL AND AUGMENTED REALITY AND METHODS FOR DISPLAYINGIMAGES USING SAME.” The contents of the aforementioned patentapplications are hereby expressly and fully incorporated by reference intheir entirety, as though set forth in full.

BACKGROUND

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, wherein digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves presentation of digital or virtual image informationwithout transparency to other actual real-world visual input; anaugmented reality, or “AR”, scenario typically involves presentation ofdigital or virtual image information as an augmentation to visualizationof the actual world around the user (i.e., transparency to other actualreal-world visual input). Accordingly, AR scenarios involve presentationof digital or virtual image information with transparency to otheractual real-world visual input. The human visual perception system isvery complex, and producing a VR or AR technology that facilitates acomfortable, natural-feeling, rich presentation of virtual imageelements amongst other virtual or real-world imagery elements ischallenging.

The visualization center of the brain gains valuable perceptioninformation from the motion of both eyes and components thereof relativeto each other. Vergence movements (i.e., rolling movements of the pupilstoward or away from each other to converge the lines of sight of theeyes to fixate upon an object) of the two eyes relative to each otherare closely associated with focusing (or “accommodation”) of the lensesof the eyes. Under normal conditions, changing the focus of the lensesof the eyes, or accommodating the eyes, to focus upon an object at adifferent distance will automatically cause a matching change invergence to the same distance, under a relationship known as the“accommodation-vergence reflex.” Likewise, a change in vergence willtrigger a matching change in accommodation, under normal conditions.Working against this reflex, as do most conventional stereoscopic AR orVR configurations, is known to produce eye fatigue, headaches, or otherforms of discomfort in users.

Stereoscopic wearable glasses generally feature two displays for theleft and right eyes that are configured to display images with slightlydifferent element presentation such that a three-dimensional perspectiveis perceived by the human visual system. Such configurations have beenfound to be uncomfortable for many users due to a mismatch betweenvergence and accommodation (“vergence-accommodation conflict”) whichmust be overcome to perceive the images in three dimensions. Indeed,some users are not able to tolerate stereoscopic configurations. Theselimitations apply to both AR and VR systems. Accordingly, mostconventional AR and VR systems are not optimally suited for presenting arich, binocular, three-dimensional experience in a manner that will becomfortable and maximally useful to the user, in part because priorsystems fail to address some of the fundamental aspects of the humanperception system, including the vergence-accommodation conflict.

AR and/or VR systems must also be capable of displaying virtual digitalcontent at various perceived positions and distances relative to theuser. The design of AR and/or VR systems also presents numerous otherchallenges, including the speed of the system in delivering virtualdigital content, quality of virtual digital content, eye relief of theuser (addressing the vergence-accommodation conflict), size andportability of the system, and other system and optical challenges.

One possible approach to address these problems (including thevergence-accommodation conflict) is to project light at the eyes of auser using a plurality of light-guiding optical elements such that thelight and images rendered by the light appear to originate from multipledepth planes. The light-guiding optical elements are designed toin-couple virtual light corresponding to digital or virtual objects andpropagate it by total internal reflection (“TIR”), then to out-couplethe virtual light to display the digital or virtual objects to theuser's eyes. In AR systems, the light-guiding optical elements are alsodesigned be transparent to light from (e.g., reflecting off of) actualreal-world objects. Therefore, portions of the light-guiding opticalelements are designed to reflect virtual light for propagation via TIRwhile being transparent to real-world light from real-world objects inAR systems.

To implement multiple light-guiding optical element systems, light fromone or more sources must be controllably distributed to each of thelight-guiding optical element systems. One approach is to use a largenumber of optical elements (e.g., light sources, prisms, gratings,filters, scan-optics, beam splitters, mirrors, half-mirrors, shutters,eye pieces, etc.) to project images at a sufficiently large number(e.g., six) of depth planes. The problem with this approach is thatusing a large number of components in this manner necessarily requires alarger form factor than is desirable, and limits the degree to which thesystem size can be reduced. The large number of optical elements inthese systems also results in a longer optical path, over which thelight and the information contained therein will be degraded. Thesedesign issues result in cumbersome systems which are also powerintensive. The systems and methods described herein are configured toaddress these challenges.

SUMMARY

Embodiments of the present invention are directed to devices, systemsand methods for facilitating virtual reality and/or augmented realityinteraction for one or more users.

In one embodiment, an imaging system includes a light source configuredto generate a light beam. The system also includes first and secondlight guiding optical elements having respective first and second entryportions, and configured to propagate at least respective first andsecond portions of the light beam by total internal reflection. Thesystem further includes a light distributor having a light distributorentry portion, a first exit portion, and a second exit portion. Thelight distributor is configured to direct the first and second portionsof the light beam toward the first and second entry portions,respectively. The light distributor entry portion and the first exitportion are aligned along a first axis. The light distributor entryportion and the second exit portion are aligned along a second axisdifferent from the first axis.

In one or more embodiments, the first and second light guiding opticalelements and the light distributor are configured such that when thelight beam interacts with the first exit portion, a first exit beamletof the light beam exits the light distributor and enters the first lightguiding optical element via the first entry portion, and when the lightbeam interacts with the second exit portion, a second exit beamlet ofthe light beam exits the light distributor and enters the second lightguiding optical element via the second entry portion. The system mayalso include first and second shutters configured to selectivelyinterrupt first and second light paths between first and second exitportions and first and second entry portions, respectively. The firstand second light guiding optical elements may be disposed on oppositesides of the light distributor.

In one or more embodiments, the system also includes a focusingdiffractive optical element disposed between the first and second lightguiding optical elements. The focusing diffractive optical element maybe configured to focus the second exit beamlet of the light beam towardthe second entry portion of the second light guiding optical element.

In one or more embodiments, the first exit portion is a first beamsplitter, and wherein the second exit portion is a second beam splitter.The first and second beam splitters may have different sizes. The firstand second entry portions may have different sizes corresponding to thedifferent sizes of the first and second beam splitters. The lightdistributor entry portion may be a receiving beam splitter configured todivide the light beam into first and second split beamlets respectivelydirected to the first and second beam splitters.

In one or more embodiments, the receiving beam splitter is a dichroicbeam splitter. The first split beamlet may include green light and thesecond split beamlet includes red and blue light.

In one or more embodiments, the receiving beam splitter is a polarizingbeam splitter, and wherein the light beam comprises polarized light. Thepolarized light may include green light. The light distributor may alsohave a retardation filter configured to change a polarization angle of aportion of the light beam. The portion of the light beam may includeblue light.

In one or more embodiments, the receiving beam splitter is an X-cubebeam splitter.

In one or more embodiments, the system also includes a third beamsplitter disposed along the first axis such that the first beam splitteris between the light distributor beam splitter and the third beamsplitter. The first beam splitter may be a dichroic beam splitterconfigured to divide the light beam into first and second splitbeamlets. The first and third beam splitters may be configured such thatthe first split beamlet is directed toward the first entry portion andthe second split beamlet is directed toward the third beam splitter. Thefirst split beamlet may include green light and the second split beamletmay include red and blue light.

In one or more embodiments, the first beam splitter is a polarizing beamsplitter, and wherein the light beam comprises polarized light. Thepolarized light may include green light. The light distributor may alsohave a retardation filter configured to change a polarization angle of aportion of the light beam. The portion of the light beam may includeblue light.

In another embodiment, an imaging system includes a light sourceconfigured to generate a light beam. The system also includes a firstlight guiding optical element having a first entry portion andconfigured to propagate at least a first portion of the light beam bytotal internal reflection. The system further includes a second lightguiding optical element having a second entry portion and configured topropagate at least a second portion of the light beam by total internalreflection. Moreover, the system includes a light distributor having alight distributor entry portion, a first exit portion and a second exitportion, and configured to direct at least portions of the light beaminto the first and second light guiding optical elements. The lightdistributor entry portion is disposed between the first and second exitportions.

In one or more embodiments, the light distributor entry portion is adichroic beam splitter. The light distributor entry portion may be anX-cube beam splitter.

In still another embodiment, an imaging system includes a light sourceconfigured to generate a light beam. The system also includes a firstlight guiding optical element having a first entry portion andconfigured to propagate at least a first portion of the light beam bytotal internal reflection. The system further includes a second lightguiding optical element having a second entry portion and configured topropagate at least a second portion of the light beam by total internalreflection. Moreover, the system includes a light distributor having afirst out-coupling grating and a second out-coupling grating. The firstand second light guiding optical elements and the light distributor areconfigured such that when the light beam interacts with the firstout-coupling grating, a first exit beamlet of the light beam exits thelight distributor and enters the first light guiding optical element viathe first entry portion, and when the light beam interacts with thesecond out-coupling grating, a second exit beamlet of the light beamexits the light distributor and enters the second light guiding opticalelement via the second entry portion.

In one or more embodiments, the first out-coupling grating is a dynamicor static grating. The second out-coupling grating may be a dynamic orstatic grating.

In yet another embodiment, an imaging system includes a light sourceconfigured to generate a parent light beam. The system also includes alight guiding optical element configured to propagate at least a portionof the light beam by total internal reflection. The light sourceincludes a beam splitter configured to divide the parent light beam intofirst and second light beams.

In one or more embodiments, the system also includes first and secondshutters configured to selectively block first and second light beams,respectively.

In still another embodiment, an imaging system includes a light sourceconfigured to generate a parent light beam. The system also includes afirst light guiding optical element configured to propagate a firstportion of the light beam by total internal reflection. The systemfurther includes a second light guiding optical element configured topropagate a second portion of the light beam by total internalreflection. The first portion of the light beam includes green light,and the second portion of the light beam includes red and blue light.The first and second light guiding optical elements are configured todirect the first and second portions of the light beam to first andsecond eyes of a user. The first and second light guiding opticalelements are also configured to render first and second images at thesame depth plane.

In yet another embodiment, an imaging system includes a light sourceconfigured to generate a parent light beam. The system also includes afirst light guiding optical element having an entry portion andconfigured to propagate at least a portion of the light beam by totalinternal reflection. The system further includes a second light guidingoptical element. Moreover, the system includes a reflective coatingdisposed on a surface of the second light guiding optical elementadjacent the first light guiding optical element. The reflective coatingis configured to reflect light passing through the entry portion back atthe entry portion.

Additional and other objects, features, and advantages of the inventionare described in the detail description, figures and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of various embodiments ofthe present invention. It should be noted that the figures are not drawnto scale and that elements of similar structures or functions arerepresented by like reference numerals throughout the figures. In orderto better appreciate how to obtain the above-recited and otheradvantages and objects of various embodiments of the invention, a moredetailed description of the present inventions briefly described abovewill be rendered by reference to specific embodiments thereof, which areillustrated in the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIGS. 1 to 3 are detailed schematic views of various optical systems;

FIG. 4 is a diagram depicting the focal planes of an optical system;

FIG. 5 is a detailed schematic view of a light-guiding optical elementof an optical system;

FIG. 6 is a detailed perspective view of a light-guiding optical elementof an optical system;

FIG. 7 is a detailed schematic view of an optical system;

FIG. 8 is a detailed schematic view of an optical system according toone embodiment;

FIG. 9 is a detailed perspective view of an optical system according toone embodiment;

FIG. 10 is a top view of the light distributor of the optical systemdepicted in FIG. 9;

FIG. 11 is a top view of a light distributor according to oneembodiment;

FIG. 12 is a detailed perspective view of an optical system according toone embodiment;

FIGS. 13 to 15 are detailed schematic views of optical systems accordingto two embodiments;

FIG. 16 is a detailed perspective view of an optical system according toone embodiment;

FIG. 17 is a detailed schematic view of an optical system according toone embodiment;

FIGS. 18 and 19 are detailed schematic views of optical systemsaccording to two embodiments;

FIG. 20 is a top view of a light distributor according to oneembodiment;

FIGS. 21, 22 and 23 are detailed perspective, top, and side views of anoptical system according to one embodiment;

FIG. 24 is a detailed perspective view of an optical system according toone embodiment;

FIG. 25 is a detailed perspective view of a light distributor accordingto one embodiment;

FIG. 26 is a schematic view of an optical system according to oneembodiment;

FIG. 27 is a schematic view of a light guiding optical element and twolight distributors configured for use with the optical system depictedin FIG. 26;

FIGS. 28 and 29 are schematic views of optical systems according to twoembodiments.

DETAILED DESCRIPTION

Various embodiments of the invention are directed to systems, methods,and articles of manufacture for implementing optical systems in a singleembodiment or in multiple embodiments. Other objects, features, andadvantages of the invention are described in the detailed description,figures, and claims.

Various embodiments will now be described in detail with reference tothe drawings, which are provided as illustrative examples of theinvention so as to enable those skilled in the art to practice theinvention. Notably, the figures and the examples below are not meant tolimit the scope of the present invention. Where certain elements of thepresent invention may be partially or fully implemented using knowncomponents (or methods or processes), only those portions of such knowncomponents (or methods or processes) that are necessary for anunderstanding of the present invention will be described, and thedetailed descriptions of other portions of such known components (ormethods or processes) will be omitted so as not to obscure theinvention. Further, various embodiments encompass present and futureknown equivalents to the components referred to herein by way ofillustration.

The optical systems may be implemented independently of AR systems, butmany embodiments below are described in relation to AR systems forillustrative purposes only.

Summary of Problem and Solution

One type of optical system for generating images at various depthsincludes numerous optical components (e.g., light sources, prisms,gratings, filters, scan-optics, beam splitters, mirrors, half-mirrors,shutters, eye pieces, etc.) that increase in number, thereby increasingthe complexity, size and cost of AR and VR systems, as the quality ofthe 3D experience/scenario (e.g., the number of imaging planes) and thequality of images (e.g., the number of image colors) increases. Theincreasing size of optical systems with increasing 3D scenario/imagequality imposes a limit on the size of AR and VR systems resulting incumbersome systems with reduced efficiency.

The following disclosure describes various embodiments of systems andmethods for creating 3D perception using multiple-plane focus opticalelements that address the problem, by providing optical systems withfewer components and increased efficiency. In particular, the systemsdescribed herein utilize various light distribution systems, includingvarious system components and designs, to reduce the size of opticalsystems while selectively distributing light from one or more lightsources to the plurality of light-guiding optical elements (“LOEs”;e.g., planar waveguides) required to render high quality AR and VRscenarios.

Illustrative Optical Systems

Before describing the details of embodiments of the light distributionsystems, this disclosure will now provide a brief description ofillustrative optical systems. While the embodiments are can be used withany optical system, specific systems (e.g., AR systems) are described toillustrate the technologies underlying the embodiments.

One possible approach to implementing an AR system uses a plurality ofvolume phase holograms, surface-relief holograms, or light-guidingoptical elements that are embedded with depth plane information togenerate images that appear to originate from respective depth planes.In other words, a diffraction pattern, or diffractive optical element(“DOE”) may be embedded within or imprinted upon an LOE such that ascollimated light (light beams with substantially planar wavefronts) issubstantially totally internally reflected along the LOE, it intersectsthe diffraction pattern at multiple locations and exits toward theuser's eye. The DOEs are configured so that light exiting therethroughfrom an LOE are verged so that they appear to originate from aparticular depth plane. The collimated light may be generated using anoptical condensing lens (a “condenser”).

For example, a first LOE may be configured to deliver collimated lightto the eye that appears to originate from the optical infinity depthplane (0 diopters). Another LOE may be configured to deliver collimatedlight that appears to originate from a distance of 2 meters (½ diopter).Yet another LOE may be configured to deliver collimated light thatappears to originate from a distance of 1 meter (1 diopter). By using astacked LOE assembly, it can be appreciated that multiple depth planesmay be created, with each LOE configured to display images that appearto originate from a particular depth plane. It should be appreciatedthat the stack may include any number of LOEs. However, at least Nstacked LOEs are required to generate N depth planes. Further, N, 2N or3N stacked LOEs may be used to generate RGB colored images at N depthplanes.

In order to present 3D virtual content to the user, the augmentedreality (AR) system projects images of the virtual content into theuser's eye so that they appear to originate from various depth planes inthe Z direction (i.e., orthogonally away from the user's eye). In otherwords, the virtual content may not only change in the X and Y directions(i.e., in a 2D plane orthogonal to a central visual axis of the user'seye), but it may also appear to change in the Z direction such that theuser may perceive an object to be very close or at an infinite distanceor any distance in between. In other embodiments, the user may perceivemultiple objects simultaneously at different depth planes. For example,the user may see a virtual dragon appear from infinity and run towardsthe user. Alternatively, the user may simultaneously see a virtual birdat a distance of 3 meters away from the user and a virtual coffee cup atarm's length (about 1 meter) from the user.

Multiple-plane focus systems create a perception of variable depth byprojecting images on some or all of a plurality of depth planes locatedat respective fixed distances in the Z direction from the user's eye.Referring now to FIG. 4, it should be appreciated that multiple-planefocus systems typically display frames at fixed depth planes 202 (e.g.,the six depth planes 202 shown in FIG. 4). Although AR systems caninclude any number of depth planes 202, one exemplary multiple-planefocus system has six fixed depth planes 202 in the Z direction. Ingenerating virtual content one or more of the six depth planes 202, 3Dperception is created such that the user perceives one or more virtualobjects at varying distances from the user's eye. Given that the humaneye is more sensitive to objects that are closer in distance thanobjects that appear to be far away, more depth planes 202 are generatedcloser to the eye, as shown in FIG. 4. In other embodiments, the depthplanes 202 may be placed at equal distances away from each other.

Depth plane positions 202 are typically measured in diopters, which is aunit of optical power equal to the inverse of the focal length measuredin meters. For example, in one embodiment, depth plane 1 may be ⅓diopters away, depth plane 2 may be 0.3 diopters away, depth plane 3 maybe 0.2 diopters away, depth plane 4 may be 0.15 diopters away, depthplane 5 may be 0.1 diopters away, and depth plane 6 may representinfinity (i.e., 0 diopters away). It should be appreciated that otherembodiments may generate depth planes 202 at other distances/diopters.Thus, in generating virtual content at strategically placed depth planes202, the user is able to perceive virtual objects in three dimensions.For example, the user may perceive a first virtual object as being closeto him when displayed in depth plane 1, while another virtual objectappears at infinity at depth plane 6. Alternatively, the virtual objectmay first be displayed at depth plane 6, then depth plane 5, and so onuntil the virtual object appears very close to the user. It should beappreciated that the above examples are significantly simplified forillustrative purposes. In another embodiment, all six depth planes maybe concentrated on a particular focal distance away from the user. Forexample, if the virtual content to be displayed is a coffee cup half ameter away from the user, all six depth planes could be generated atvarious cross-sections of the coffee cup, giving the user a highlygranulated 3D view of the coffee cup.

In one embodiment, the AR system may work as a multiple-plane focussystem. In other words, all six LOEs may be illuminated simultaneously,such that images appearing to originate from six fixed depth planes aregenerated in rapid succession with the light sources rapidly conveyingimage information to LOE 1, then LOE 2, then LOE 3 and so on. Forexample, a portion of the desired image, comprising an image of the skyat optical infinity may be injected at time 1 and the LOE 1090 retainingcollimation of light (e.g., depth plane 6 from FIG. 4) may be utilized.Then an image of a closer tree branch may be injected at time 2 and anLOE 1090 configured to create an image appearing to originate from adepth plane 10 meters away (e.g., depth plane 5 from FIG. 4) may beutilized; then an image of a pen may be injected at time 3 and an LOE1090 configured to create an image appearing to originate from a depthplane 1 meter away may be utilized. This type of paradigm can berepeated in rapid time sequential (e.g., at 360 Hz) fashion such thatthe user's eye and brain (e.g., visual cortex) perceives the input to beall part of the same image.

AR systems are required to project images (i.e., by diverging orconverging light beams) that appear to originate from various locationsalong the Z axis (i.e., depth planes) to generate images for a 3Dexperience. As used in this application, light beams including, but arenot limited to, directional projections of light energy (includingvisible and invisible light energy) radiating from a light source.Generating images that appear to originate from various depth planesconforms the vergence and accommodation of the user's eye for thatimage, and minimizes or eliminates vergence-accommodation conflict.

FIG. 1 depicts a basic optical system 100 for projecting images at asingle depth plane. The system 100 includes a light source 120 and anLOE 190 having a diffractive optical element (not shown) and anin-coupling grating 192 (“ICG”) associated therewith. The light source120 can be any suitable imaging light source, including, but not limitedto DLP, LCOS, LCD and Fiber Scanned Display. Such light sources can beused with any of the systems 100 described herein. The diffractiveoptical elements may be of any type, including volumetric or surfacerelief. The ICG 192 can be a reflection-mode aluminized portion of theLOE 190. Alternatively, the ICG 192 can be a transmissive diffractiveportion of the LOE 190. When the system 100 is in use, a virtual lightbeam 210 from the light source 120, enters the LOE 190 via the ICG 192and propagates along the LOE 190 by substantially total internalreflection (“TIR”) for display to an eye of a user. The light beam 210is virtual because it encodes an image or a portion thereof as directedby the system 100. It is understood that although only one beam isillustrated in FIG. 1, a multitude of beams, which encode an image, mayenter LOE 190 from a wide range of angles through the same ICG 192. Alight beam “entering” or being “admitted” into an LOE includes, but isnot limited to, the light beam interacting with the LOE so as topropagate along the LOE by substantially TIR. The system 100 depicted inFIG. 1 can include various light sources 120 (e.g., LEDs, OLEDs, lasers,and masked broad-area/broad-band emitters). Light from the light source120 may also be delivered to the LOE 190 via fiber optic cables (notshown).

FIG. 2 depicts another optical system 100′, which includes a lightsource 120, and respective pluralities (e.g., three) of LOEs 190, andin-coupling gratings 192. The optical system 100′ also includes threebeam splitters 162 (to direct light to the respective LOEs) and threeshutters 164 (to control when the LOEs are illuminated). The shutters164 can be any suitable optical shutter, including, but not limited to,liquid crystal shutters. The beam splitters 162 and shutters 164 aredepicted schematically in FIG. 2 without specifying a configuration toillustrate the function of optical system 100′. The embodimentsdescribed below include specific optical element configurations thataddress various issues with optical systems.

When the system 100′ is in use, the virtual light beam 210 from thelight source 120 is split into three virtual light sub-beams/beamlets210′ by the three-beam splitters 162. The three beam splitters alsoredirect the beamlets toward respective in-coupling gratings 192. Afterthe beamlets enter the LOEs 190 through the respective in-couplinggratings 192, they propagate along the LOEs 190 by substantially TIR(not shown) where they interact with additional optical structuresresulting in display to an eye of a user. The surface of in-couplinggratings 192 on the far side of the optical path can be coated with anopaque material (e.g., aluminum) to prevent light from passing throughthe in-coupling gratings 192 to the next LOE 190. The beam splitters 162can be combined with wavelength filters to generate red, green and bluebeamlets. Three single-color LOEs 190 are required to display a colorimage at a single depth plane. Alternatively, LOEs 190 may each presenta portion of a larger, single depth-plane image area angularly displacedlaterally within the user's field of view, either of like colors, ordifferent colors (“tiled field of view”). While all three virtual lightbeamlets 210′ are depicted as passing through respective shutters 164,typically only one beamlet 210′ is selectively allowed to pass through acorresponding shutter 164 at any one time. In this way, the system 100′can coordinate image information encoded by the beam 210 and beamlet210′ with the LOE 190 through which the beamlet 210 and the imageinformation encoded therein will be delivered to the user's eye.

FIG. 3 depicts still another optical system 100″, having respectivepluralities (e.g., six) of beam splitters 162, shutters 164, ICGs 192,and LOEs 190. As explained above during the discussion of FIG. 2, threesingle-color LOEs 190 are required to display a color image at a singledepth plane. Therefore, the six LOEs 190 of this system 100″ are able todisplay color images at two depth planes. The beam splitters 162 inoptical system 100″ have different sizes. The shutters 164 in opticalsystem 100″ have different sizes corresponding to the size of therespective beam splitters 162.

The ICGs 192 in optical system 100″ have different sizes correspondingto the size of the respective beam splitters 162 and the length of thebeam path between the beam splitters 162 and their respective ICGs 192.The longer the distance beam path between the beam splitters 162 andtheir respective ICGs 192, the more the beams diverge and require alarger ICGs 192 to in-couple the light. As shown in FIG. 3, larger beamsplitters 162 also require larger ICGs 192. While larger beam splitters162 allow light sources 120 to have larger scan angles, and thus largerfields of view (“FOVs”), they also require larger ICGs 192, which aresusceptible to a “second encounter problem.”

The Second Encounter Problem

The second encounter problem is depicted in FIG. 3. The virtual lightbeamlet 210′ depicted in FIG. 3 enters an LOE 190 through an ICG 192.The size of ICG 192 is such that as the beamlet 210′ propagates throughthe LOE 190 by TIR, the beamlet 210′ encounters the ICG 192 at a secondlocation 212. This second encounter allows unintended out-coupling oflight from the LOE 190, thereby decreasing the intensity of the lightpropagated along the LOE 190. Accordingly, increasing the size of an ICG192 such that a beamlet 210′ has a second encounter with the ICG 192during TIR will decrease the efficiency of the optical system 100″ forselect LOEs 190. Embodiments addressing the second encounter problem aredescribed below.

While this problem is described as a “second” encounter problem, largerICGs 192 can cause a series of repeat encounters that would furtherdecrease the optical efficiency. Further, as shown in FIGS. 1-4, as thenumber of depth planes, field tiles, or colors generated increases(e.g., with increased AR scenario quality), the numbers of LOEs 190 andICGs 192 increases. For example, a single RGB color depth plane requiresat least three single-color LOEs 190 with three ICGs 192. As a result,the opportunity for inadvertent in-coupling of real-world light at theseoptical elements also increases. Moreover, real-world light can bein-coupled all along an LOE 190, including at out-coupling gratings (notshown). Thus the increasing number of optical elements required togenerate an acceptable AR scenario exacerbates the second encounterproblem for the system 100.

Pupil Expanders

As shown in FIG. 5, portions of the LOEs 190 described above canfunction as exit pupil expanders 196 (“EPE”) to increase the numericalaperture of a light source 120 in the Y direction, thereby increasingthe resolution of the system 100. Since the light source 120 produceslight of a small diameter/spot size, the EPE 196 expands the apparentsize of the pupil of light exiting from the LOE 190 to increase thesystem resolution. The AR system 100 may further comprise an orthogonalpupil expander 194 (“OPE”) in addition to an EPE 196 to expand the lightin both the X (OPE) and Y (EPE) directions. More details about the EPEs196 and OPEs 194 are described in the above-referenced U.S. Utilitypatent application Ser. No. 14/555,585 and U.S. Utility patentapplication Ser. No. 14/726,424, the contents of which have beenpreviously incorporated by reference.

FIG. 5 depicts an LOE 190 having an ICG 192, an OPE 194 and an EPE 196.FIG. 5 depicts the LOE 190 from a top view that is similar to the viewfrom a user's eyes. The ICG 192, OPE 194, and EPE 196 may be any type ofDOE, including volumetric or surface relief.

The ICG 192 is a DOE (e.g., a linear grating) that is configured toadmit a virtual light beam 210 from a light source 120 for propagationby TIR. In the system 100 depicted in FIG. 5, the light source 120 isdisposed to the side of the LOE 190.

The OPE 194 is a DOE (e.g., a linear grating) that is slanted in thelateral plane (i.e., perpendicular to the light path) such that avirtual light beam 210 that is propagating through the system 100 willbe deflected by 90 degrees laterally. The OPE 194 is also partiallytransparent and partially reflective along the light path, so that thelight beam 210 partially passes through the OPE 194 to form multiple(e.g., eleven) beamlets 210′. In the depicted system 100, the light pathis along an X axis, and the OPE 194 configured to bend the beamlets 210′to the Y axis.

The EPE 196 is a DOE (e.g., a linear grating) that is slanted in a Zplane (i.e., normal to the X and Y directions) such that the beamlets210′ that are propagating through the system 100 will be deflected by 90degrees in the Z plane and toward a user's eye. The EPE 196 is alsopartially transparent and partially reflective along the light path (theY axis), so that the beamlets 210′ partially pass through the EPE 196 toform multiple (e.g., seven) beamlets 210′. Only select beams 210 andbeamlets 210′ are labeled for clarity.

The OPE 194 and the EPE 196 are both also at least partially transparentalong the Z axis to allow real-world light (e.g., reflecting offreal-world objects) to pass through the OPE 194 and the EPE 196 in the Zdirection to reach the user's eyes. For AR systems 100, the ICG 192 isat least partially transparent along the Z axis also at least partiallytransparent along the Z axis to admit real-world light. However, whenthe ICG 192, OPE 194, or the EPE 196 are transmissive diffractiveportions of the LOE 190, they may unintentionally in-couple real-worldlight may into the LOE 190. As described above this unintentionallyin-coupled real-world light may be out-coupled into the eyes of the userforming ghost artifacts.

FIG. 6 depicts another optical system 100 including an LOE 190 having anICG 192, an OPE 194, and an EPE 196. The system 100 also includes alight source 120 configured to direct a virtual light beam 210 into theLOE 190 via the ICG 192. The light beam 210 is divided into beamlets210′ by the OPE 194 and the EPE 196 as described with respect to FIG. 5above. Further, as the beamlets 210′ propagate through the EPE 196, theyalso exit the LOE 190 via the EPE 196 toward the user's eye. Only selectbeams 210 and beamlets 210′ are labeled for clarity.

Multiple Depth Optical Systems

FIG. 7 depicts an optical system 100 including a plurality (e.g., four)of LOEs 190, each having an ICG 192, an OPE 194, and an EPE 196. Each ofthe plurality of LOEs 190 can be configured to deliver light to a user'seye such that the light has a particular color and/or appears tooriginate from a particular depth plane. The system 100 also includes alight source 120 configured to direct a virtual light beam 210 into alight distributor 300. The light distributor 300 is configured to dividethe light beam 210 into a plurality (e.g., four) of beamlets 210′ and todirect the beamlets 210′ toward respective shutters 164 and respectiveICGs 192 behind the shutters 164.

The light distributor 300 has a plurality (e.g., four) of beam splitters162. The beam splitters 162 can be of any type, including, but notlimited to, partially reflective beam splitters, dichroic beam splitters(e.g., dichroic mirror prisms), and/or polarizing beam splitters, suchas wire-grid beam splitters. In the system 100 depicted in FIG. 7, onlyone shutter 164 is open to allow only one beamlet 210′ to address itsrespective ICG 192 and propagate through its respective LOE 190 by TIR.The beam splitters 162 and shutters 164 are depicted schematically inFIG. 7 without specifying a configuration to illustrate the function ofoptical system 100. The embodiments described below include specificoptical element configurations that address various issues with opticalsystems.

The beamlet 210′ is further divided into beamlets 210′ by the OPE 194and the EPE 196 as described above with respect to FIG. 6. The beamlets210′ also exit the LOE 190 via the EPE 196 toward the user's eye asdescribed above. Only select duplicate system components, beams 210 andbeamlets 210′ are labeled for clarity.

Further, the ICG 192 is depicted on the top surface of the top LOE 190and on the sides of each of the four LOEs 190 in the system 100. Thisside view demonstrates that the ICG 192 of each of the stack of LOEs 190is disposed in a different location on the face of its LOE 190 to alloweach ICG 192 in the stack of LOEs 190 to be addressed by a separate beamsplitter 162 in the distribution device. Because each beam splitter 162is separated by its respective ICG 192 by a controllable shutter, thesystem 100 can select one LOE 190 to be illuminated by a beamlet 210′ ata particular time. While the locations of the schematically illustratedshutters 164 and ICGs 192 appear to vary only along the X axis, thelocations can vary along any spatial axis (X, Y, or Z).

FIG. 8 depicts an optical system 100 according to one embodiment, whichincludes a plurality (e.g., five) of LOEs 190, each having an ICG 192,an OPE 194, and an EPE 196. Each of the plurality of LOEs 190 can beconfigured to deliver light to a user's eye such that the light has aparticular color and/or appears to originate from a particular depthplane. The system 100 also includes a light source 120 configured todirect a virtual light beam 210 into a light distributor 300. The lightdistributor 300 is configured to divide the light beam 210 into aplurality (e.g., five) of beamlets 210′ and to direct the beamlets 210′toward respective shutters 164 and respective ICGs 192 behind theshutters 164.

The light distributor 300 depicted in FIG. 8 is an integral opticalelement having an ICG 192 and a plurality (e.g., five) of out-couplinggratings 302 (“OCG”). The ICG 192 is configured to in-couple a virtuallight beam 210 from the light source 120 such that it propagates bysubstantially TIR in the light distributor 300. The OCGs can be dynamicgratings (e.g., PDLC) or static gratings. The OCGs 302 are disposedserially along the longitudinal axis and TIR light path of the lightdistributor 300. Each of the OCGs is configured to direct a portion(e.g., a beamlet 210′) of the light beam 210 near a tangent to the lightdistributor 300 and out of the light distributor 300 and toward arespective ICG 192 in a respective LOE 190. Another portion of the beam210 reflects off of the OCG 302 at a more oblique angle, and continuesto propagate through the light distributor by substantially TIR. Thisother portion of the beam 210 interacts with the remaining plurality ofOCGs 302, which correspond to each of the LOEs 190 in the system 100.

Like the system 100 depicted in FIG. 7, the system 100 depicted in FIG.8 also includes a plurality (e.g., five) of shutters 164 separating thelight distributor 300 from respective ICGs 192. While the locations ofthe schematically illustrated OCGs 302, shutters 164, and ICGs 192appear to vary only along the X axis, the locations can vary along anyspatial axis (X, Y, or Z).

As described above, the light distributor 300 is configured to dividethe virtual light beam 210 into a plurality (e.g., five) of beamlets210′. While each OCG 302 depicted in FIG. 8 redirects a beamlet 210′toward an opposite side of the light distributor 300 for exit, an OCG302 may also allow a beamlet 210′ to exit therethrough in otherembodiments. In such embodiments, the OCGs 302 can be disposed on thesurface of the light distributor adjacent the shutters 164 and LOEs 190.In the system 100 depicted in FIG. 8, only one shutter 164 is open toallow only one beamlet 210′ to address its respective ICG 192 andpropagate through its respective LOE 190 by TIR. However, the otherbeamlets 210′ are depicted as passing through their respective closedshutters 164 to illustrate their paths.

The beamlet 210′ is further divided into beamlets 210′ by the OPE 194and the EPE 196 as described above with respect to FIG. 6. The beamlets210′ also exit the LOE 190 via the EPE 196 toward the user's eye asdescribed above. Only select duplicate system components, beams 210 andbeamlets 210′ are labeled for clarity.

Further, the ICG 192 is depicted on the top surface of the top LOE 190and on the sides of all on the LOEs 190. This side view demonstratesthat the ICG 192 of each of the stack of LOEs 190 is disposed in adifferent location on the face of its LOE 190 to allow each ICG 192 inthe stack of LOEs 190 to be addressed by a separate beam splitter 162 inthe distribution device. Because each beam splitter 162 is separated byits respective ICG 192 by a controllable shutter, the system 100 canselect one LOE 190 to be illuminated by a beamlet 210′ at a particulartime.

The system depicted in FIG. 8 also includes an optional focusing opticalelement 304, which addresses the second encounter problem describedabove, by focusing the diverging beamlets 210′ at an LOE 190 between thelight distributor 300 and the corresponding ICG 192 in the correspondingLOE 190. Focusing the diverging beamlets 210′ at the focusing opticalelement 304 causes the beamlets 210′ to converged onto the ICG 192,thereby reducing the size of the ICG 192 required to in-couple the fullrange of beamlets 210′ delivered by the light distributor 300.

FIG. 9 depicts an optical system 100 according to another embodiment,which includes a plurality (e.g., four) of LOEs 190, each having an ICG192, an OPE 194, and an EPE 196. Each of the plurality of LOEs 190 canbe configured to deliver light to a user's eye such that the light has aparticular color and/or appears to originate from a particular depthplane. The system 100 also includes a light source 120 configured todirect a virtual light beam 210 into a light distributor 300. The lightdistributor 300 is configured to divide the light beam 210 into aplurality (e.g., four) of beamlets 210′, and to direct the beamlets 210′toward respective shutters 164 and respective ICGs 192 behind theshutters 164.

The light distributor 300 has a plurality (e.g., five) of beam splitters162 arranged in an “L” shape. The “L” shape is formed from anin-coupling beam splitter 308 and two “arms” 306 connected thereto. Eachof the arms 306 includes two beam splitters 162. The beam splitters 162in the arms 306 can be of any type, including, but not limited to,partially reflective beam splitters, dichroic beam splitters (e.g.,dichroic mirror prisms), or polarizing beam splitters, such as awire-grid beam splitter. Dichroic and polarizing beam splitters separatelight based on wavelength (i.e., color) and polarization, respectively.While the in-coupling beam splitter 308 in this embodiment is apartially reflective beam splitter (e.g., 50% reflective and 50%transmissive), the in-coupling beam splitter 308 in other embodimentscan be dichroic or polarizing beam splitters.

The in-coupling beam splitter 308 is configured to admit the virtuallight beam 210 from the light source 120, and divide it into twobeamlets 210′ for propagation by TIR along the two arms 306. The twobeamlets 210′ propagate through the arms 306 and interact with the beamsplitters 162 therein in a similar fashion to as the beam 210 interactswith the beam splitters 162 in the light distributor 300 depicted inFIG. 7. While the shutters 164 in FIG. 9 are depicted as closed, theyare configured to open one at a time to allow only one beamlet 210′ toaddress its respective ICG 192 and propagate through its respective LOE190 by TIR. In the LOE 190, the beamlet 210′ is further divided intobeamlets 210′ by the OPE 194 and the EPE 196 as described above withrespect to FIG. 6. The beamlets 210′ also exit the LOE 190 via the EPE196 toward the user's eye as described above. Only select duplicatesystem components, beams 210 and beamlets 210′ are labeled for clarity.Because each beam splitter 162 is separated by its respective ICG 192 bya controllable shutter, the system 100 can select one LOE 190 to beilluminated by a beamlet 210′ at a particular time.

The “L” shape of the light distributor 300 depicted in FIG. 9 results inthe positioning of the shutters 164 in an approximate “L” shape in thesystem 100 depicted in FIG. 9. The “L” shape of the light distributor300 also results in the positioning of the ICGs 192 in an approximate“L” shape in the system 100 depicted in FIG. 9. The “L” shape depictedin FIG. 9 is a more compact spatial distribution of ICGs 192 compared tothe linear shape depicted in FIG. 7. The “L” shape also provides feweropportunities for inadvertent in-coupling of light from adjacent ICGs192. Both of these features are evident from FIG. 10, which is a topview of the light distributor 300 depicted in FIG. 9.

FIG. 11 is a top view of the light distributor 300 according to stillanother embodiment. In the light distributor 300 the in-coupling beamsplitter 308 and the beam splitters 162 that form the arms 306 are ofdifferent sizes. The larger beam splitters 162, 308 can accommodatelight having larger scan angles and concomitant larger FOVs. The size ofthe beam splitters 162 can be optimized based on the scan anglerequirements of the LOE 190 corresponding to the beam splitter 162. Forinstance, the system 100 and/or beam splitter 162 sizes can be optimizedby balancing at least the following scan angle considerations/metrics:the number and size of LOEs 190 in the system 100; maximizing FOV size;maximizing exit pupil size; reducing second encounter problem (e.g., byreducing ICG 192 size).

The shapes of the light distributors 300 in FIGS. 9 to 11 requirecorresponding arrangements of shutters 164 and ICGs in the LOEs 190 ofthe systems 100. Also, the shapes of the light distributors 300 resultin particular positional relationships between the light sources 120 andthe light distributors 300, which in turn result in correspondingoverall system profiles.

FIG. 12 depicts an optical system 100 according to yet anotherembodiment. The system 100 in FIG. 12 is almost identical to the onedepicted in FIG. 9. The difference is the addition of a secondin-coupling beam splitter 308′. The second in-couple beam splitter 308′is configured to allow the light source 120 to address the lightdistributor 300 from below the plane of the light distributor 300instead of in the plane of the light distributor 300, as in FIG. 9. Thisdesign change allows the light source 120, which may be sizeable in someembodiments, to be located in a different position in the system 100.

FIG. 13 schematically depicts an optical system 100 according to anotherembodiment. In this embodiment, the light distributor 300 is formed ofbeam splitters 162 having different sizes, which allows optimization ofthe system 100 according to the scan angle requirements of the LOE 190corresponding to the beam splitter 162. In some embodiments, the system100 and/or beam splitter 162 sizes can be optimized by balancing atleast the following scan angle considerations/metrics: the number andsize of LOEs 190 in the system 100; maximizing FOV size; maximizing exitpupil size; reducing second encounter problem (e.g., by reducing ICG 192size). For instance, a first beam splitter 162-1 is a cube with a sidelength of 1.5 mm. The corresponding first shutter 164-1 has a length of1.5 mm. A second beam splitter 162-2 is a cube with a side length of 1mm. The corresponding second shutter 164-2 has a length of 1 mm. A thirdbeam splitter 162-3 is a cube with a side length of 1.5 mm. Thecorresponding third shutter 164-3 has a length of 1.2 mm. A fourth beamsplitter 162-4 is a cube with a side length of 2 mm. The correspondingfourth shutter 164-4 has a length of 1.8 mm.

The system 100 also includes respective pluralities (e.g., four) of LOEs190 and ICGs 192 corresponding thereto. As shown in FIG. 13, the size(e.g., length) of the shutters 164 and ICGs 192 are a function of thedistances between (1) the light source 120 and the corresponding beamsplitter 162 and (2) the corresponding beam splitter and thecorresponding ICG 192. This is because these distances will determinewhether the virtual light beams 210 and beamlets 210′ are converging ordiverging when they interact with the beam splitter 162, the shutter164, and ICGs 192. Only select beams 210 and beamlets 210′ are labeledfor clarity. While the shutters 164 in FIG. 13 are depicted as closed,they are configured to open one at a time to allow only one beamlet 210′to address its respective ICG 192 and propagate through its respectiveLOE 190 by TIR. The beamlets 210′ in FIG. 13 are depicted as passingthrough their respective closed shutters 164 to illustrate their paths.

FIG. 14 schematically depicts an optical system 100 according to stillanother embodiment. Like the light distributor depicted in FIG. 13, thelight distributor 300 depicted in FIG. 14 is formed of beam splitters162 having different sizes, which allows optimization of the system 100according to the scan angle requirements of the LOE 190 corresponding tothe beam splitter 162. For instance, the system 100 and/or beam splitter162 sizes can be optimized by balancing at least the following scanangle considerations/metrics: the number and size of LOEs 190 in thesystem 100; maximizing FOV size; maximizing exit pupil size; reducingsecond encounter problem (e.g., by reducing ICG 192 size). Unlike thesystem 100 depicted in FIG. 13, the system 100 depicted in FIG. 14includes LOEs 190 and shutters 164 disposed on opposite sides of thebeam splitters 162. This configuration shortens the light path for someLOEs 190, thereby reducing the size of the corresponding ICGs 192 fordiverging light beamlets 210′. Reducing the size of ICGs 192 improvesoptical efficiency by avoiding the second encounter problem. DisposingLOEs 190 (and shutters 164) on opposite sides of the beam splitters 162requires some of the beam splitters 162-1, 162-2 to direct light in afirst orthogonal direction and other beam splitters 162-3, 162-4 todirect light in a second orthogonal direction opposite

Only select beams 210 and beamlets 210′ in FIG. 14 are labeled forclarity. While the shutters 164 in FIG. 14 are depicted as closed, theyare configured to open one at a time to allow only one beamlet 210′ toaddress its respective ICG 192 and propagate through its respective LOE190 by TIR. The beamlets 210′ in FIG. 14 are depicted as passing throughtheir respective closed shutters 164 to illustrate their paths.

FIGS. 15 and 16 depict optical systems 100 according to two otherembodiments. The systems 100 depicted in FIGS. 15 and 16 are similar tothe systems 100 depicted in FIGS. 9 and 12, because the systems 100depicted in FIGS. 9, 12, 15, and 16 each have four LOEs 190. Thedifferences in the systems 100 are driven by the differentconfigurations of the light distributors 300 therein. The lightdistributor 300 in FIG. 15 has two parallel arms 306 (formed of beamsplitters 162) that are connected by an in-coupling beam splitter 308and offset from each other in the X and Y axes. The light distributor300 in FIG. 16 has two perpendicular arms 306 (formed of beam splitters162) that are connected by an in-coupling beam splitter 308 and offsetfrom each other in the Y axis.

The different configurations of the light distributors 300 in FIGS. 15and 16 lead to differences in the configurations of the shutters 164(only shown in FIG. 16) and LOEs 190. The different light distributor300, shutter 164, and LOE 190 configurations can be used to customizethe three dimensional footprint of the optical system 100 to provide aparticular device form factor. Only select system components, beams 210and beamlets 210′ are included and labeled in FIGS. 15 and 16 forclarity. While the shutters 164 in FIG. 16 are depicted as closed, theyare configured to open one at a time to allow only one beamlet 210′ toaddress its respective ICG 192 and propagate through its respective LOE190 by TIR.

FIG. 17 schematically depicts an optical system 100 according to anotherembodiment, which has a plurality (e.g., five) LOEs 190. The system 100depicted in FIG. 17 is similar to the system 100 depicted in FIG. 14because the system 100 includes LOEs 190 and shutters 164 disposed onopposite sides of the beam splitters 162. As described above, thisconfiguration shortens the light path for some LOEs 190, therebyreducing the size of the corresponding ICGs 192 for diverging lightbeamlets 210′ and reducing the second encounter problem.

The main difference between the systems 100 depicted in FIGS. 14 and 17is that the light distributor 300 depicted in FIG. 17 is an integraloptical element instead of a plurality of beam splitters 162, as shownin FIG. 14. The light distributor 300 in FIG. 17 includes an irregularlyshaped DOE 310 that is configured to divide the virtual light beam 210into a plurality (e.g., five) beamlets 210′ and to direct those beamlets210′ toward respective shutters 164 and respective ICGs 192 behind theshutters 164. Portions of the irregularly shaped DOE 310 are configuredto direct beamlets 210′ having a larger size or scanning angle, therebyincreasing the resolution of the system 100.

Only select system components, beams 210 and beamlets 210′ are includedand labeled in FIG. 17 for clarity. While the shutters 164 in FIG. 17are depicted as closed, they are configured to open one at a time toallow only one beamlet 210′ to address its respective ICG 192 andpropagate through its respective LOE 190 by TIR.

FIGS. 18 to 20 depict optical systems 100 and light distributors 300located therein according to three other embodiments. The systems 100and light distributors 300 depicted in FIGS. 18 to 20 are similar to thesystems 100 and light distributors 300 depicted in FIGS. 9, 12, 15, and16, however the systems 100 each have different light distributor 300and LOE 190 configurations. The systems 100 and light distributors 300depicted in FIGS. 18 to 20 are similar to each other because they allaccommodate six channels for six LOEs. Since three single-color LOEs 190are required to display a color image at a single depth plane, the sixLOEs 190 of these systems 100 can display color images at two depthplanes.

The differences in the systems 100 depicted in FIGS. 18 to 20 (and FIGS.9, 12, 15, and 16) are driven by the different configurations of thelight distributors 300 therein. The light distributor 300 in FIG. 18 hasthree arms 306-1, 306-2, 306-3 (formed of beam splitters 162) that areconnected by two in-coupling beam splitters 308. Two of the arms 306-1,306-2 are parallel but offset from each other in the Y and Z axes. Theother arm 306-3 is perpendicular to the first two arms 306-1, 306-2 andoffset from the other two arms 306-1, 306-2 in the X and Y axes. Thebeam splitters 162 in the arms 306-1, 306-2, 306-3 can be of any type,including, but not limited to, partially reflective beam splitters,dichroic beam splitters (e.g., dichroic mirror prisms), or polarizingbeam splitters, such as a wire-grid beam splitter. While the in-couplingbeam splitters 308 in this embodiment are partially reflective beamsplitters, the in-coupling beam splitter 308 in other embodiments can bedichroic or polarizing beam splitters.

The light distributor 300 in FIG. 19 has two arms 306-1, 306-2 (formedof beam splitters 162) that are connected by an in-coupling beamsplitter 308. The arms 306-1, 306-2 are disposed on one axis with thein-coupling beam splitter 308 therebetween. The in-coupling beamsplitter 308 is an X-cube beam splitter configured to direct half of thelight beam 210 into the first arm 306-1 and the other half into thesecond arm 306-2. Some of the beam splitters 162 in the arms 306-1,306-2 can be polarizing beam splitters configured to redirect only onecolor of light based on it polarization.

For instance, the first beam splitter 162-1 adjacent the in-couplingbeam splitter 308 (in each of the first and second arms 306-1, 306-2)can be configured to redirect green light (with 0 degrees polarization)out of the beam splitter 162-1 while allowing red and blue (each with 90degrees polarization) light to proceed through the beam splitter 162-1.A retardation filter 312 is disposed between the first beam splitter162-1 and the second beam splitter 162-2. The retardation filter 312 isconfigured to change the polarization of only the red light from 90degrees to 0 degrees, leaving the blue light with 90 degreespolarization. The second beam splitter 162-2 can be configured toredirect red light (with 0 degrees polarization after passing throughretardation filter 312) out of the beam splitter 162-2 but allow blue(with 90 degrees polarization) light to proceed through the beamsplitter 162-2. The third “beam splitter” 162-3 can be replaced with asimple 45 degree mirror. Alternatively, the third beam splitter 162-3can be dichroic beam splitter configured to redirect blue light out ofthe beam splitter 162-3.

The light distributor 300 in FIG. 20 has three arms 306-1, 306-2, 306-3(formed of beam splitters 162) that are connected by an in-coupling beamsplitter 308. The arms 306-1, 306-2, 306-3 form a “T” shape rotated 90degrees counterclockwise with the in-coupling beam splitter 308 at thejunction of the “T” shape. The in-coupling beam splitter 308 is adichroic beam splitter or dichroic mirror prism configured to direct redlight into the first arm 306-1 and blue light into the third arm 306-3,and to allow green light to pass through into the second arm 306-2. Eachbeam splitter 162 can be partially reflective to direct a portion of thecolored light out of the beam splitter and into the corresponding LOE(not shown).

The dichroic beam splitters, dichroic mirror prisms, polarization beamsplitters, and retardation filters can be used to design various lightdistributors 300 configured to generate beamlets 210′ with a particularcolor.

The different configurations of the light distributors 300 in FIGS. 18to 20 lead to differences in the configurations of the shutters 164 andLOEs 190 (only shown in FIGS. 18 and 19). The different lightdistributor 300, shutter 164, and LOE 190 configurations can be used tocustomize the three dimensional footprint of the optical system 100 toprovide a particular device form factor. Only select system components,beams 210 and beamlets 210′ are included and labeled in FIGS. 18 to 20for clarity. While the shutters 164 in FIG. 16 are depicted as closed,they are configured to open one at a time to allow only one beamlet 210′to address its respective ICG 192 and propagate through its respectiveLOE 190 by TIR.

FIGS. 21 to 23 depict an optical system 100, from perspective, top, andside views respectively, according to another embodiment. The system 100and light distributor 300 depicted in FIGS. 21 to 23 are similar to thesystems 100 and light distributors 300 depicted in FIGS. 9, 12, 15, 16,and 18 to 20, however the systems 100 each have different lightdistributor 300 and LOE 190 configurations. The systems 100 and lightdistributors 300 depicted in FIGS. 21 to 23 are similar to thosedepicted in FIGS. 18 to 20 because they all accommodate six channels forsix LOEs.

The light distributor 300 depicted in depicted in FIGS. 21 to 23 has twoarms 306-1, 306-2 (formed of beam splitters 162) that are connected bytwo in-coupling beam splitters 308. The arms 306-1, 306-2 are parallelbut offset from each other in the Z axis. The in-coupling beam splitters308 are partially reflective beam splitters configured to direct half ofthe light beam 210 into the first arm 306-1 and the other half into thesecond arm 306-2. The second in-coupling “beam splitter” 308 can bereplaced with a simple 45 degree mirror. Some of the beam splitters 162in the arms 306-1, 306-2 can be polarizing beam splitters configured toredirect only one color of light based on it polarization.

For instance, a first retardation filter 312 is disposed between thein-coupling beam splitters 308 and the first beam splitter 162-1. Thefirst retardation filter 312 is configured to change the polarization ofred and blue light from 0 degrees to 90 degrees, while leaving thepolarization of green light at 0 degrees. The first beam splitter 162-1adjacent the in-coupling beam splitter 308 and the first retardationfilter 312 can be configured to redirect green light (with 0 degreespolarization) out of the beam splitter 162-1 but allow red and blue(each with 90 degrees polarization) light to proceed through the beamsplitter 162-1.

A second retardation filter 312 is disposed between the first beamsplitter 162-1 and the second beam splitter 162-2. The secondretardation filter 312 is configured to change the polarization of onlyred light from 90 degrees to 0 degrees, leaving blue light with 90degrees polarization. The second beam splitter 162-2 can be configuredto redirect red light (with 0 degrees polarization after passing throughsecond retardation filter 312) out of the beam splitter 162-2 but allowblue light (with 90 degrees polarization) to proceed through the beamsplitter 162-2. The third “beam splitter” 162-3 can be a simple 45degree mirror. Alternatively, the third beam splitter 162-3 can bedichroic beam splitter configured to redirect blue light out of the beamsplitter 162-3. A half-wave plate 314 is disposed between the third beamsplitter 162-3 and the LOE 190 to restore the blue light to 0 degreespolarization. The beam splitters 162-1, 162-2, 162-3 in both the firstand second arms 306-1, 306-2 function in a similar manner.

FIG. 24 depicts an optical system 100 according to another embodiment.The system 100 depicted in FIG. 24 is similar to the system 100 depictedin FIGS. 21 to 23, however the light distributors 300 in the systems 100have beam splitters 162 with different aspect ratios. The beam splitters162 depicted in FIGS. 21 to 23 are cubes with equal sides (e.g., 3 mm).The beam splitters 162 depicted in FIG. 24 are 3 mm by 3 mm by 5 mm. The5 mm size in the Z direction means that the faces of the beam splitters162 through which light is directed (i.e., the Y-Z plane and the X-Zplane) have a 3 by 5 aspect ratio. This aspect ratio provides adirectional increase in scan angle.

FIG. 25 depicts a light distributor 300 similar to the one depicted inFIG. 24 in that the beam splitters 162 in both light distributors 300have a 3 by 5 aspect ratio. However, while the two in-coupling beamsplitters 308 in FIG. 24 are effectively the same size, the twoin-coupling beam splitters 308 in FIG. 25 have different sizes. Forinstance, the first in-coupling beam splitter 308-1 in FIG. 25 is 5 mm×3mm×5 mm, and the second in-coupling beam splitter 308-2 is 5 mm×3 mm×3mm. Changing the size of the in-coupling beam splitters 308 changes thescan angles of the two arms 306-1, 306-2.

FIG. 26 depicts an optical system 100 according to another embodiment.The system 100 includes a plurality of LOEs 190, first and second lightdistributors 300-1, 300-2, and a dual beam light source 120. The dualbeam light source 120 is configured to divide a single virtual lightbeam 210 into two spatially separated beamlets 210′ that can be directedinto first and second light distributors 300-1, 300-2, respectively. Thedual beam light source 120 includes two beam splitters 162, two shutters164, and various focusing optical elements 316. The beam splitters 162can be of any type, including, but not limited to, partially reflectivebeam splitters, dichroic beam splitters (e.g., dichroic mirror prisms),or polarizing beam splitters, such as a wire-grid beam splitter. Movingtwo beam splitters 162 and shutters 164 from the light distributor 300into the light source 120, and splitting one light distributor 300 intotwo light distributors 300-1, 300-2 changes the overall systemconfiguration and form factor.

FIG. 27 depicts a plurality of LOEs 190 and two light distributors300-1, 300-2 according to another embodiment and configured for use withthe system 100 depicted in FIG. 26. The light distributors 300-1, 300-2in FIG. 27 include respective in-coupling beam splitters 308 that arelarger than the size of the beam splitters forming the lightdistributors 300-1, 300-2 to allow larger scan angles.

FIG. 28 schematically depicts an optical system 100 according to yetanother embodiment. This system 100 combines the red and blue light intoone LOE 190 to reduce the number of LOEs 190 needed to render anacceptable color image at one depth plane from three to two.Accordingly, the system 100 depicted in FIG. 28 generates acceptablefull color images at four depth planes using eight LOEs 190 instead oftwelve. This reduction in the number of LOEs 190 and correspondingoptical elements (e.g., lenses, beam splitters 162, shutters 164, etc.)reduces the overall size of the system 100.

FIG. 29 depicts an optical system 100 according to another embodiment.The system 100 depicted in FIG. 29 addresses the inadvertentout-coupling problem. The system 100 includes a light source 120 andthree LOEs 190. The light source 120 is configured to direct a virtuallight beam 210 toward an ICG 192 of a first LOE 190-1. While the ICG 192is configured to direct the beam 210 into the first LOE 190-1 topropagate by TIR therethrough, only a first portion of the beam 210′ isdirected into the first LOE 190-1. Because ICG 192 efficiency is lessthan 100% (e.g., 50%), a second portion of the beam 210″ passes throughthe ICG 192 and out of the first LOE 190-1. This second portion of thebeam 210″ can escape the system 100, as shown by the dotted line 210′″in FIG. 29, thereby reducing optical efficiency and beam density.

The system 100 in FIG. 29 addresses this problem by disposing a mirrorcoating 318 on the other side of the light source 120 from the ICG 192.In particular, the mirror coating 318 is disposed on the side of asecond LOE 190-2 that is closest to the ICG 192. The mirror coating 318and the ICG 192 are configured such that the second portion of the beam210″ reflects off of the mirror coating 318 and re-enters the ICG 192 ofthe first LOE 190-1. This light 210″ is in-coupled into the first LOE190-1 and propagates therethrough by TIR, thereby increasing the opticalefficiency and beam density of the system 100.

While some embodiments are described as using retardation filters 312,polarizing beam splitters 162, and half-wave plates 314 to configurelight distributors 300 for redirection light of different colors, thespecific embodiments are only illustrative and not meant to be limiting.Accordingly, such light distributors 300 can be configured to outputcolored light in any color order.

While some embodiments are described as having four channels, thosesystems can still be used to render acceptable full color virtual imagesat two depth planes because blue and red light can be delivered usingthe same channel to two LOEs. Optical systems using a single blue/redchannel design to reduce the number of components are described in theabove-referenced U.S. Prov. Patent Application Ser. No. 62/156,809, thecontents of which have been previously incorporated by reference. Usingthis design, two channels (Green and Red/Blue) can be used to render anacceptable full color virtual image at one depth plane.

The above-described AR systems are provided as examples of variousoptical systems that can benefit from more selectively reflectiveoptical elements. Accordingly, use of the optical systems describedherein is not limited to the disclosed AR systems, but rather applicableto any optical system.

Various exemplary embodiments of the invention are described herein.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the invention.Various changes may be made to the invention described and equivalentsmay be substituted without departing from the true spirit and scope ofthe invention. In addition, many modifications may be made to adapt aparticular situation, material, composition of matter, process, processact(s) or step(s) to the objective(s), spirit or scope of the presentinvention. Further, as will be appreciated by those with skill in theart that each of the individual variations described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentinventions. All such modifications are intended to be within the scopeof claims associated with this disclosure.

The invention includes methods that may be performed using the subjectdevices. The methods may comprise the act of providing such a suitabledevice. Such provision may be performed by the end user. In other words,the “providing” act merely requires the end user obtain, access,approach, position, set-up, activate, power-up or otherwise act toprovide the requisite device in the subject method. Methods recitedherein may be carried out in any order of the recited events which islogically possible, as well as in the recited order of events.

Exemplary aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally known or appreciated by those with skill in the art. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the true spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation.

Without the use of such exclusive terminology, the term “comprising” inclaims associated with this disclosure shall allow for the inclusion ofany additional element—irrespective of whether a given number ofelements are enumerated in such claims, or the addition of a featurecould be regarded as transforming the nature of an element set forth insuch claims. Except as specifically defined herein, all technical andscientific terms used herein are to be given as broad a commonlyunderstood meaning as possible while maintaining claim validity.

The breadth of the present invention is not to be limited to theexamples provided and/or the subject specification, but rather only bythe scope of claim language associated with this disclosure.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Forexample, the above-described process flows are described with referenceto a particular ordering of process actions. However, the ordering ofmany of the described process actions may be changed without affectingthe scope or operation of the invention. The specification and drawingsare, accordingly, to be regarded in an illustrative rather thanrestrictive sense.

1. An imaging system, comprising: a light source configured to generatea light beam; a first light guiding optical element including a firstentry portion and configured to propagate at least a first portion ofthe light beam by total internal reflection; a second light guidingoptical element including a second entry portion and configured topropagate at least a second portion of the light beam by total internalreflection; and a light distributor including a light distributor entryportion, a first exit portion and a second exit portion, the lightdistributor configured to direct at least the first and second portionsof the light beam into the first and second light guiding opticalelements, respectively, wherein the light distributor entry portion isdisposed between the first and second exit portions.
 2. The system ofclaim 1, wherein the first and second light guiding optical elements andthe light distributor are configured such that: when the light beaminteracts with the first exit portion, a first exit beamlet of the lightbeam exits the light distributor and enters the first light guidingoptical element via the first entry portion, and when the light beaminteracts with the second exit portion, a second exit beamlet of thelight beam exits the light distributor and enters the second lightguiding optical element via the second entry portion.
 3. The system ofclaim 1, further comprising first and second shutters configured toselectively interrupt first and second light paths between first andsecond exit portions and first and second entry portions, respectively.4. The system of claim 1, wherein the first and second light guidingoptical elements are disposed on opposite sides of the lightdistributor.
 5. The system of claim 1, further comprising a focusingdiffractive optical element disposed between the first and second lightguiding optical elements, wherein the focusing diffractive opticalelement is configured to focus the second exit beamlet of the light beamtoward the second entry portion of the second light guiding opticalelement.
 6. The system of claim 1, wherein the first exit portion is afirst beam splitter, and wherein the second exit portion is a secondbeam splitter.
 7. The system of claim 6, wherein the first and secondbeam splitters have different sizes.
 8. The system of claim 7, whereinthe first and second entry portions have different sizes correspondingto the different sizes of the first and second beam splitters.
 9. Thesystem of claim 6, where the light distributor entry portion is areceiving beam splitter configured to divide the light beam into firstand second split beamlets respectively directed to the first and secondbeam splitters.
 10. The system of claim 9, wherein the receiving beamsplitter is a dichroic beam splitter.
 11. The system of claim 10,wherein the first split beamlet includes green light and the secondsplit beamlet includes red and blue light.
 12. The system of claim 9,wherein the receiving beam splitter is a polarizing beam splitter, andwherein the light beam comprises polarized light.
 13. The system ofclaim 12, wherein the polarized light includes green light, wherein thelight distributor also has a retardation filter configured to change apolarization angle of a portion of the light beam, and wherein theportion of the light beam includes blue light.
 14. The system of claim9, wherein the receiving beam splitter is an X-cube beam splitter. 15.The system of claim 6, further comprising a third beam splitter disposedbetween the first beam splitter and the light distributor beam splitter.16. The system of claim 1, further comprising a first out-couplinggrating and a second out-coupling grating, wherein the first and secondlight guiding optical elements and the light distributor are configuredsuch that: when the light beam interacts with the first out-couplinggrating, a first exit beamlet of the light beam exits the lightdistributor and enters the first light guiding optical element via thefirst entry portion, and when the light beam interacts with the secondout-coupling grating, a second exit beamlet of the light beam exits thelight distributor and enters the second light guiding optical elementvia the second entry portion.
 17. The system of claim 16, wherein thefirst out-coupling grating is a dynamic grating.
 18. The system of claim16, wherein the first out-coupling grating is a static grating.
 19. Thesystem of claim 1, further comprising a third light guiding opticalelement including a third entry portion and configured to propagate atleast a third portion of the light beam by total internal reflection,wherein the light distributor also a third exit portion, and wherein thelight distributor is configured to direct at least the first, second,and third portions of the light beam into the first, second, and thirdlight guiding optical elements, respectively.
 20. The system of claim19, wherein the first portion of the light beam is red, wherein thesecond portion of the light beam is green, and wherein the third portionof the light beam is blue.